Process hazards explosions

Have formal process hazard analyses (PHAs) been completed for highly hazardous processes (for example, those processes involving toxic or volatile substances, highly toxic materials, severe lachrymators, flammables, explosive compounds or potential runaway reactions) If yes, please summarize status of each. 

Complete and accurate written documentation of chemicals properties, process teclinology, and process equipment is essential to the PSM program and to a process hazards analysis (PrHA). This information serves many users including the PrHA team. The needed chemical information includes fire and explosion characteristics, reactivity hazards, safety and health hazards and the corrosion and erosion effects. Current material safety data sheet (MSDS ) information helps meet this requirement, but must be supplemented with process chemistry information regarding runaway reactions, and over-pressure hazards. 

The results of previous process hazards evaluations may be used if it can be confirmed that the reviews adequately addressed explosion and fire risks to process plant buildings. ... 

The index works out at 21 classified as Fight . Ammonia would not normally be considered a dangerously flammable material the danger of an internal explosion in the reactor is the main process hazard. The toxicity of ammonia and the corrosiveness of nitric acid would also need to be considered in a full hazard evaluation. 

The procedure begins with a material factor that is a function only of the type of chemical or chemicals used. This factor is adjusted for general and special process hazards. These adjustments or penalties are based on conditions such as storage above the flash or boiling point, endo- or exothermic reactions, and fired heaters. Credits for various safety systems and procedures are used for estimating the consequences of the hazard, after the fire and explosion index has been determined. 

The Mond Index (ICI, 1985) has been developed from the 1973 version of the Dow F E Index. The principal modifications to the Dow method include (Lees, 1996) 1) wider range of processes and storage installations can be studied, 2) covers processing of chemicals having explosive properties, 3) improved hazard consideration for hydrogen, 4) additional special process hazards, 5) toxicity included into the assesment. 

The frequently used Dow Fire Explosion Hazard Index (1987) gives penalties for fired equipment and certain specified rotating equipment. These are a part of the Special Process Hazards term of the Dow Index. 

Chemical Exposure Index (CEI) (Chemical Exposure Index, 1994 Mannan, 2005, pp. 8/22-8/26.) The CEI provides a method of rating the relative potential of acute health hazard to people from possible chemical release incidents. It may be used for prioritizing initial process hazard analysis and establishing the degree of further analysis needed. The CEI also may be used as part of the site review process. The system provides a method of ranking one risk relative to another. It is not intended to define a particular containment system as safe or unsafe, but provides a way of comparing toxic hazards. It deals with acute, not chronic, releases. Flammability and explosion hazards are not included in this index. To develop a CEI, information needs include... 

During the development of a new facility or process, or when introducing a new process into an existing facility for the first time, an inherent safety review can be conducted to understand the chemical reactivity hazards and explore hazard reduction alternatives. The review need not be limited to chemical reactivity hazards. It can be used to address all other types of process hazards at the same time, including flammability/ combustibility dust or mist explosibility elevated or reduced pressures or temperatures phase differences and health hazards such as toxicity, corrosivity, and asphyxiation. 

Several qualitative approaches can be used to identify hazardous reaction scenarios, including process hazard analysis, checklists, chemical interaction matrices, and an experience-based review. CCPS (1995a p. 176) describes nine hazard evaluation procedures that can be used to identify hazardous reaction scenarios-checklists, Dow fire and explosion indices, preliminary hazard analysis, what-if analysis, failure modes and effects analysis (FMEA), HAZOP study, fault tree analysis, human error analysis, and quantitative risk analysis. 

PHAST (Process Hazard Analysis Software Tool)—This is a conglomerate package for gas dispersion and fire modeling. PHAST is capable of calculating the formation of a cloud or pool to final dispersion calculating concentrations, fire radiation, toxicity, and explosion overpressure endpoints. 

American Petroleum Institute Recommended Practice. In 1990, the American Petroleum Institute issued a recommended practice on Management of Process Hazards (35). The stated objective was to help prevent the occurrence of, or minimize the consequences of, catastrophic releases of toxic, flammable, or explosive materials. 

Process Hazards Contributing to Fire and Explosion Incidents ... 

Predictive hazard evaluation procedures may be required when new and different processes, designs, equipment, or procedures are being contemplated. The Dow Fire and Explosion Index provides a direct method to estimate the risks in a chemical process based upon flammability and reactivity characteristics of the chemicals, general process hazards (as exothermic reactions, indoor storage of flammable liquids, etc.) and special hazards (as operation above the flash point, operation above the auto-ignition point, quantity of flammable liquid, etc.). Proper description of this index is best found in the 57-page Dows Fire and Explosion Index, Hazard Classification Guide, 5 th ed., AIChE, New York, 1981. 

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